Case Study: Long Wave Pass Dichroic Filter

Case Study: Case Study: Steep Long Wave Pass Dichroic Filter at 45 Deg. AOI

Customer Challenge: The customer has a system with a range of 10 LEDs 4 requiring reflection and 6 of a higher wavelength range requiring Transmission at right angles to each other. The filter needed to reflect and transmit quite a wide bandwidth into each channel of the instrument.

Vortex’s Solution: A steep edge dichroic filter operating at 45˚angle of incidence (AOI), was required. Our approach was to design the filter first and send an excel spreadsheet of data for the proposed filter to the customer for review. With the initial consultation over, manufacture could then proceed, a batch of 10 samples was sent initially to allow the customer to practically test the dichroic within the system, see T and R graph below for performance. The remaining could be supplied on a call off basis over the rest of the year.

The Result: The filter was manufactured using our state of the art sputtering technology to the tolerance of +/-5 nm. The other important property was to ensue lack of thermal drift, even when the filter temperature was raised to 100˚C, there was <0.2nm movement of the edge position. Uniformity was also excellent on the sample, i.e. all areas met the customer specification. We were also able to satisfy the steepness tolerance, to ensure efficient transmission and reflection of all LEDs, see spectral graphs above.